350 research outputs found
Understanding Anthropological Understanding: for a merological anthropology
In this paper I argue for a merological anthropology in which ideas of ‘partiality’ and ‘practical adequacy’ provide a way out of the impasse of relativism which is implied by post-modernism and the related abandonment of a concern with ‘truth’. Ideas such as ‘aptness’ and ‘faithfulness’ enable us to re-establish empirical foundations without having to espouse a simple realism which has been rightly criticised. Ideas taken from ethnomethodology, particularly the way we bootstrap from ‘practical adequacy’ to ‘warrants for confidence’ point to a merological anthropology in which we recognize that we do not and cannot know everything, but that we can have reasons for being confident in the little we know
Breakdown of correspondence in chaotic systems: Ehrenfest versus localization times
Breakdown of quantum-classical correspondence is studied on an experimentally
realizable example of one-dimensional periodically driven system. Two relevant
time scales are identified in this system: the short Ehrenfest time t_h and the
typically much longer localization time scale T_L. It is shown that
surprisingly weak modification of the Hamiltonian may eliminate the more
dramatic symptoms of localization without effecting the more subtle but
ubiquitous and rapid loss of correspondence at t_h.Comment: 4 pages, 5 figures, replaced with a version submitted to PR
Scaling laws for the 2d 8-state Potts model with Fixed Boundary Conditions
We study the effects of frozen boundaries in a Monte Carlo simulation near a
first order phase transition. Recent theoretical analysis of the dynamics of
first order phase transitions has enabled to state the scaling laws governing
the critical regime of the transition. We check these new scaling laws
performing a Monte Carlo simulation of the 2d, 8-state spin Potts model. In
particular, our results support a pseudo-critical beta finite-size scaling of
the form beta(infinity) + a/L + b/L^2, instead of beta(infinity) + c/L^d +
d/L^{2d}. Moreover, our value for the latent heat is 0.294(11), which does not
coincide with the latent heat analytically derived for the same model if
periodic boundary conditions are assumed, which is 0.486358...Comment: 10 pages, 3 postscript figure
Donor states in modulation-doped Si/SiGe heterostructures
We present a unified approach for calculating the properties of shallow
donors inside or outside heterostructure quantum wells. The method allows us to
obtain not only the binding energies of all localized states of any symmetry,
but also the energy width of the resonant states which may appear when a
localized state becomes degenerate with the continuous quantum well subbands.
The approach is non-variational, and we are therefore also able to evaluate the
wave functions. This is used to calculate the optical absorption spectrum,
which is strongly non-isotropic due to the selection rules. The results
obtained from calculations for Si/SiGe quantum wells allow us to
present the general behavior of the impurity states, as the donor position is
varied from the center of the well to deep inside the barrier. The influence on
the donor ground state from both the central-cell effect and the strain arising
from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure
The (im)materiality of literacy : the significance of subjectivity to new literacies research.
This article deconstructs the online and offline experience to show its complexities and idiosyncratic nature. It proposes a theoretical framework designed to conceptualise aspects of meaning-making across on- and offline contexts. In arguing for the ‘(im)materiality’ of literacy, it makes four propositions which highlight the complex and diverse relationships between the immaterial and material associated with meaning-making. Complementing existing sociocultural perspectives on literacy, the article draws attention to the significance of relationships between space, mediation, materiality and embodiment to literacy practices. This in turn emphasises the importance of the subjective in understanding how different locations, experiences and so forth inflect literacy practice. The article concludes by drawing on the Deleuzian concept of the ‘baroque’ to suggest that this focus on articulations between the material and immaterial helps us to see literacy as multiply and flexibly situated
A note on the Sagnac effect and current terrestrial experiments
We focus on the Sagnac effect for light beams in order to evaluate if the higher-order relativistic corrections of kinematic origin could be relevant for actual terrestrial experiments. Moreover, we discuss to what extent the analogy with the Aharonov-Bohm effect holds true in a fully relativistic framework. We show that the analogy with the Aharonov-Bohm is not true in general, but is recovered in a suitable low-order approximation, and that even though the Sagnac effect is influenced by both the position of the interferometer in the rotating frame and its extension, these effects are negligible for current terrestrial experiment
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
We review basic theoretical concepts in particle acceleration, with
particular emphasis on processes likely to occur in regions of magnetic
reconnection. Several new developments are discussed, including detailed
studies of reconnection in three-dimensional magnetic field configurations
(e.g., current sheets, collapsing traps, separatrix regions) and stochastic
acceleration in a turbulent environment. Fluid, test-particle, and
particle-in-cell approaches are used and results compared. While these studies
show considerable promise in accounting for the various observational
manifestations of solar flares, they are limited by a number of factors, mostly
relating to available computational power. Not the least of these issues is the
need to explicitly incorporate the electrodynamic feedback of the accelerated
particles themselves on the environment in which they are accelerated. A brief
prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
A selected bibliography on parameter optimization methods suitable for hybrid computation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68333/2/10.1177_003754976700800610.pd
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
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